Laser diodes, and particularly Vertical Cavity Surface Emitting Laser (VCSEL) diodes, are used for data transmission on optical links. Prior art drivers provide a bias current to the laser diodes. A modulation current then turns the laser diode on and off. The rise and fall times of the modulation current to the laser diode are equal. Unfortunately, the laser diode is faster to respond to a rising edge than a falling edge. As a result, there is a mismatch in the rise and fall times of the output optical pulse. This asymmetrical shape may degrade the bit error rate of the optical communication link and cause other problems.
Thus there exists a need for a circuit for driving a laser diode that provides equal rise and fall times on the output optical pulse.